How much protein, carbs and fats you need depends on your age, height, activity level and numerous other factors. There is not a single math formula to calculate it for you. Anyways, my recommendation is to go for 2 grams of protein per kg of bodyweight. For muscle gain, you will need around 3 grams of carbs per kg of bodyweight and for fat loss, around 1.5-2 grams. Fats - go for anywhere in between 30 and 80 grams.

As far as stretchmarks are concerned, I don't think you can remove them completely. Take extra zinc and vitamin C for skin elasticity.

Go for high protein, low carb, moderate fats diet. I don't know your weight and height, but you should strive to get most carbs from complex sources such as oats and brown rice/quinoa/buckwheat, between 50 and 100 grams per day is enough if you are not tolerating them well. Try having more fats, anywhere between 50 and 150 grams per day, from olive oil, nuts, eggs, meat and fish. Protein - 2 grams per kg of bodyweight is the minimum you need for gain provided you consume enough calories from fat and carbs, 2.5 for fat loss.